1. Field of the Invention
The present invention relates to a heater.
2. Description of the Related Art
Heaters have been conventionally utilized to heat substrates in semiconductor manufacturing processes and liquid crystal manufacturing processes. Examples of such heaters include Physical Vapor Deposition (PVD) devices, Chemical Vapor Deposition (CVD) devices, and dry etching devices that usually utilize corrosive gases. Ceramics are generally utilized for substrates of the heaters in terms of corrosion resistance.
In semiconductor manufacturing processes and liquid crystal manufacturing processes, a substrate is mounted on a substrate-heating surface provided a substrate-heating member of the heater. Reactive films can be accumulated on an outer circumferential portion of the substrate. While the substrate is not adhered to the substrate-heating surface, the reactive film can be adhered to the substrate-heating surface. When the substrate is removed from the substrate-heating surface, the reactive film is hardly removed from the substrate-heating surface. By a stress generated between the reactive film and the substrate-heating surface, the reactive film can be chipped or cracked. Further, the substrate can be also chipped or cracked.
Consequently, in an attempt to prevent the reactive film from accumulating at the outer circumferential portion of the substrate, as disclosed in Japanese Patent Application Laid-open No. 2002-93894, a plurality of gas ejection ports from which gas ejects are provided on the substrate-heating surface.
While accumulation of the reactive film is reduced by increasing the amount of gas ejected from the gas ejection ports, generation of growing films on the substrate is affected. Accordingly, the amount of ejected gas cannot be increased easily. Preferably, the amount of gas ejected from each of the gas ejection ports is such an amount that reduces accumulation of the reactive film and does not affect generation of the growing film.
According to the prior techniques, however, since a plurality of gas paths are formed by drilling sintered ceramic heater, a part of ceramic is broken during cutting. It is difficult to improve the dimensional accuracy of the gas paths. The amount of gas ejected on the substrate-heating surface is varied.
An object of the present invention is to provide a heater that can reduce variations in an amount of gas ejected on a substrate-heating surface and suppress accumulation of a reactive film on the substrate-heating surface without affecting generation of a growing film on a substrate.